Possible Implications for Skin Toxicity in Large Breasted Women with the Use of Enhance Dynamic-Wedged (EDW) Tangential Fields

Purpose:It has been reported that women with large breast sizes (>300 cc) may experience increased skin toxicity when undergoing post-lumpectomy radiation therapy. Studies have shown that skin dose increases with the use of dynamic wedges during chest wall irradiations. This study will evaluate the increase in skin dose due to using hard- vs. dynamic-wedged fields for various breast volumes. We hypothesize the use of enhanced dynamic-wedged tangential radiation fields will result in clinically important changes in skin toxicity.

Methods:Three phantoms were build with breast volumes 300, 400, and 500 cc. The phantoms were CT scanned and the scans were imported to the TPS for planning. For each phantom, two dosimetrically matched plans were created, one with hard wedged tangential fields and the other using enhanced dynamic-wedges (EDW). EBT film pieces were placed on various areas on the breast surface for dose measurements. The plans were delivered to each phantom using 6x photon beams.

Results:The film data showed an increase of 151%, 22%, and 26% in skin dose due to the use of EDW for 300, 400, and 500 cc breast volumes, respectively. This increase in skin dose was between 9% - 13% of the total prescription dose for EDW and 8% - 10% for HW system. The increased skin dose was evaluated by our clinicians. An increase of 26% was deemed too large and likely to result in clinically relevant implications for skin toxicity.

Conclusion: Based on these results the use of EDW for tangential field radiation therapy of patients with large breasts may increase skin toxicity